Organic EL elements are one of the most popular display elements in recent years for having excellent characteristics of high brightness and high response speed.
In a color display panel using organic EL elements, light-emitting regions that produce three different colors of red, green and blue are disposed on a glass substrate. The light-emitting regions are configured by laminating an anode electrode film of a metal thin film, a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer of organic thin films, and an electron injection layer and a cathode electrode film of metal thin films in this order to produce a color of red, green, blue, or auxiliary yellow depending on a color-producing reagent added into the light-emitting layer.
In order to form such an organic thin film, a discharger 101 of organic material vapor, as illustrated in a perspective view of FIG. 7, is used.
The discharger 101 has vapor discharge pipes 172 in the form of a pipe. The vapor discharge pipes 172 are connected, by a supply pipe 127, to a production unit 105 in which organic material vapor is generated. When organic material vapor is supplied from the production unit 105, the organic material vapor is discharged from discharge orifices 173 formed in a large number on the vapor discharge pipes 172 in a longitudinal direction thereof towards an object to be film-formed 107, and when the vapor reaches the object to be film-formed 107; an organic thin film is formed on the surface.
However, in the above discharger 101, the amount of the organic material vapor discharged from the discharge orifices 173 sometimes differs in a portion near and a portion far from the position connected to the production unit 105 within the vapor discharge pipes 172. Therefore, there is a problem of poor film thickness distribution in the organic thin film formed on the surface of the object to be film-formed 107.
Particularly when a large-scale substrate is the object to be film-formed, the object to be film-formed cannot be rotated, so that it is difficult to make the film thickness distribution uniform.
In FIG. 8, film thickness monitors 149F, 149C and 149B are disposed at positions facing a base portion (Front) near the portion connected to the supply pipe 127 of the vapor discharge pipe 172, a center portion (Center) of the vapor discharge pipe 172, and an end portion (Back) of the vapor discharge pipe 172, respectively, the end portion (Back) of the vapor discharge pipe 172 being the farthest away from the portion connected to the supply pipe 127. Only organic material vapor is introduced into the vapor discharge pipe 172 without using a carrier gas, and film thickness ratios of thin films formed at each of the positions are obtained by varying the film deposition rate.
The result is shown in Table 1 below. The film thickness of the center portion is expressed as “1”.
TABLE 1Relationship between film deposition rate and filmFilm depositionFilm thickness ratioratioBackCenterFront1 Å/s0.771.01.397 Å/s0.881.01.0815 Å/s 0.981.01.01
A graph of the film thickness distribution corresponding to Table 1 above is drawn at a position above the vapor discharge pipe 172 in FIG. 8. In FIG. 8, L is a horizontal axis that indicates the film thickness ratio “1”.
It is found that, as the film deposition rate is low (that is, as the level of the molecular flow is intensified), the film thickness ratio at the base portion becomes large.
At the film deposition rate of 15 Å/second, the film is formed generally uniformly. However, at the film deposition rate of 15 Å/second, it is difficult to control each film thickness within a desired range because it is excessively fast. At a film deposition rate greater than 7 Å/second, the formed film is prone to be nondense and a dense organic film may not be obtained. Accordingly, the film deposition rate for such an organic film is set to 7 Å/second or less, preferably from 3 Å/second to 5 Å/second.
Conventional arts that form an organic thin film using a carrier gas are shown in the following documents:
[Patent Document 1] JP 2001-523768 T,
[Patent Document 2] JP 2003-525349 T,
[Patent Document 3] JP 2004-204289 A,
[Patent Document 4] JP 2005-29885 A, and
[Patent Document 5] JP 2006-111920 A.